GB956445A - Automatic moisture content determination and control apparatus - Google Patents

Abstract

956, 445. Determination of moisture content S. SASAKI. May 11, 1960, No.16679/60. Heading G1N. An arrangement for determining the moisture content of a material such as fibre, cloth, or pulp comprises a waveguide 4 Fig. 1, including a transverse passage d through which the material 5 is passed, an oscillator 2 feeding the waveguide and a metering device 8 in which the attenuation of the oscillator signal by the material is determined by comparing the signal from a detector h which may be a crystal, with the output from a detector f at the top end of a tuning waveguide 6. The waveguides have tuners 7 and 9 at their ends, and the strength of the input signal is adjustable by an attenuator 3. The waveguide 4 comprises a hinged top portion b and the opening area of the slot beneath the hinged portion may be adjusted. The slot is lined to prevent dust from entering the waveguide and to facilitate the smooth passage of the material. A waveguide with a lateral hole for testing a yarn is described with reference to Fig. 2 not shown. In a modified circuit arrangement described with reference to Fig. 4 (not shown) the detector outputs are supplied to a single meter through a differential D. C. amplifier, the output of which may control also a steam valve for control of the moisture content. In an arrangement, Fig. 5, a reference waveguide 27 and a measuring waveguide 28 are arranged between two magic -T devices 24, 25, the former of which is fed by an oscillator 2 and includes a transfer shutter 31 driven by a motor 23 whereby the signal is applied alternatively to the two waveguides. The system is made self balancing by a two phase motor 32 adjusting an attenuator 29, the direction being governed by the phase relation between a synchronising signal produced by a rotor 30 on motor 23 in an induction coil 36, applied to field winding 34, and the rectified envelope from detector H. The action is described with reference to waveforms Fig. 6 (not shown). Balancing motor 32 is made also to drive a recording potentiometer 38 and the output to recorder 19 is applied also to a controller 20 to correct for deviations. The selection of a suitable frequency is referred to, and an example is given. Reference has been directed by the Comptroller to Specification 887, 556.